Circuit-changing mechanism



Jan. 20, 1931. P. w. BAKER CIRCUIT CHANGING MECHANISM- Filed Jan. 26. 1929 I: Inventor PA 1. w.. BAK ER Patented Jan. 20, 1931 UNITED STATES PATENT OFFICE PAUL'W. BAKER, OF 8'1. LOUIS, MISSOURI, ASSIGNOR T WAGNER ELECTRIC CORPORA- j TION, 0! 8'1. LOUIS, MISSOURI, A CORPORATION OF DELAWARE CIRCUIT-CHANGING MECHANISM My invention relates to electric motors of the kind in which the circuit changing mechanism is operated, by centrifugal means at a predetermined motor speed, the centrifugal means and a part of the mechanism actuated by it being carried by the motor shaft, and a part of the mechanism by the motor frame; It is the object of my invention to produce a circuit changing apparatus in which the elements of the centrifugally actuated mechanism which rotate during normal operation of the machine are, during such normaloperation, out of contact with the nonrotatingpart of the circuit changingapparatus which they engage and move during starting and stopping periods to change the circuit. My invention is particularly advantageous for use in vertical shaft repulsion-induction machines in which gravit tends to advance I '29 the brushholder toward t e commutator and in which therefore the contacting elements by which the short-circuiting mechanism moves the brush holder into position in which the brushes are inoperative, would, in the absence :8 of my invention, be in contact during normal operation of the machine and thus produce friction and noise since the brush holder is non-rotative and the brush holder actuating elements on the motor shaft rotate with it.

In the accompanying drawings Figure. 1 is a top plan view of a portion of a brush holder and of the associated means carried on the frame of the machine for actuating the holder in accordance with my invention;

85 Figure 2 is a cross-sectional view along the lines 22' of Figure 1, and also showing a portion of the centrifugal mechanism for moving the brush holder to bring the brushes into and out of contact with the commutator;

Figure 3 is a fragmentary view showing the relation maintained during the normal operation of the machine between the finger by means of which the brush holder is moved and the elements of the centrifugal mecha- 46 nism which actuates it during acceleration and deceleration of the machine. The mechanism on the part of the machine not illustrated in Figures 1 and 2 is a duplicate of that shown, there being two holder lifting springs, stops and the like. Figure 1 illustrates a commutator brush showlng the pigtail stiffened and bent to engage with the brush holder to limit the advancing motion of the brush in the brush holder.

In the drawings 1 represents the end plate of the machine, 2 the shaft, 3 the commutator, and 4 the brush holder adapted to slide on the hub 5 formed on the end plate. A spring 6 surrounding the shaft bears at one end against the annular collar 7 abutting the washer 8 held in a circumferential slot on the shaft and at the other end this spring bears upon the cup 9 having a radially extending flange 10. This cup 9 engages with and is seated in a recess in the sleeve 11 which carries the commutator short-circuiting elements 12. The sleeve 11 and cup 9 are, during the acceleration period of the machine, actuated by rods 13 (one only shown) through centrifugal mechanism (not shown) to compress the spring 6 and cause the sleeve 11 to contact with the finger 14 which forms an extension of the hub of the brush holder 4 and has its end turned inwardly in order that in the reverse direction of motion of the centrifugal apparatus the flange 10 of the cup 9 may contact with it to positively draw the brush holder into a position where the brushes contact with the commutator. When the brush holder has, after the normal speed of the machine has been reached, been moved upward by the centrifugal mechanism to bring the brushes out of contact with the commutator, the short-circuiting elements 12 carried in the peripheral groove in the sleeve 11 fly out under the influence of centrifugal forces into contact with the commutator segments and with the electrically conductive commutator supporting sleeve 15 and shortcircuit the commutator,

It will be noted that in the structure shown there is a lost motion connection be tween the brush holder and the centrifngally actuated elements on the shaft which con-. tact with its finger l l and this, together with the fact that the brushes will, under the influence of their follower springs 16, remain on the commutator until their motion relative to the brush holder is stopped by engagement of the pigtails with the holder, permits the commutator short-circuiting segments to come into operation before the brushes are carried out of contact with the commutator by the continued upward movement of the holder under the influence of V the centrifugal mechanism during acceleration of the machine. In order that the brush pigtails may form sufficiently rigid stops they are coated with solder to a sufficient distance from the brush and bentinto the form shown in Figure a, where the end of the solder coating is indicated at the line 20.

The mechanism so fardescribed is of known and commonly used construction in repulsion-induction motors and it will be noted that, particularly in a vertical shaft machine, the finger 14 of the brush holder, except for the means to be hereinafter described, would rest, during normal operation of the machine, upon the upperface of the periphery of the sleeve 11, and since the sleeve rotates with the shaft and the brush holder is non-rotative, the contact would result in noise and substantial frictional wear. The object of my invention is to maintain the finger 14-, during normal operation of the machine, in the position indicated in Figure 3 in which it does not contact with the face of the sleeve 11 or with the flange 10, and I accomplish this result by the provision of a spring 17 mounted on the end plate to apply suflicient lifting force to the brush holder to overcome its weight the friction between it and the hub on which it is mounted whereby it may be moved to a position limited by the stop members 18 carried by the end plate. In the form shown, the brush holder is provided with rods 19 extending from a brush holder arm to an adjacent arm and on which the springs bear.

During the normal operation of the machine the centrifugal elements which actuate the sleeve 11 and cup 9 against the spring maintain these parts in a definite position and the stops 18 are so adjusted that the movement of the brush holder by the springs 17 may not bring the finger 14 of the holder into contact with the flange 10 but will permit it to be held out of contact with the sleeve 11. Thus friction and frictional and vibrational noise, which would result from contact of the finger '14 with elements on the rotor shaft, is avoided. While a single brush lifting spring and stop might be employed it will be apparent that it is advantageous to provide two of these located on opposite sides of the shaft to avoid the canting effect on the brush holder which would be produced by the use of a single spring and thus increase the friction between the holder and its support. Also, on account of the clearance between these parts the possibility of noise originating in vibration of the holder is avoided by holding it against stops on opposite sides of the shaft.

It will be understood thatthe force of the spring 6 is made sufficient to overcome the action of the springs 17 when, during the stopping period of the machine, or at standstill,-the centrifugal mechanism no longer acts against this spring and that it will then, by actuation of the cup 9, bring the brush 10ld61" into position where the brushes will be in operative relation with the commutator.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In a dynamo electric machine, a movably mounted brush holder, centrifugally actuated means to move said brush holder, said means rotating with the shaft of the machine and having a lost motion. connection with the brush holder, other means tending to move the brush holder to move the brushes to ofl position, and means so limiting said motion that the elements forming the lost motion connection between the brush holder and the centrifugally actuated means will be maintained out of contact during the operation of the machine at or above the predetermined speed.

2. In a dynamo electric machine, a slidably mounted brush holder, centrifugally actuated means slidable on and rotating with the shaft of the machine and forming spaced parts for actuating the brush holder, means connected with the brush holder and extending between said parts to be contacted by one of them in one direction of motion of the centrifugal means and by the other in the opposite direction of motion of said means, said contacting extension being of less width than the space between said parts, spring means carried by the motor frame and adapted to and capable of moving the brush holder to inoperative position with respect to the commutator when unrestrained by the centrifugally actuated means, and a stop so limiting said motion that when the centrifugally actuated brush holder shifting means on the shaft is in its fully advanced position under condition of operation of the motor ata predetermined speed, the contacting parts of said means are out of contact with the brush holder extension.

3. In a dynamo electric machine, a slidable brush holder provided with an integral extension, centrifugally actuated means slide able on and rotating with the shaft of the machine and provided with spaced means IOU forming a lost motion connection with the brush holder extension, spring means carried by the motor frame and continuously tending to move the brush holder to inoperative position, resilient means adapted to overcome the efiect of said spring means and to continuously tend to maintain the holder in operative position, and centrifugal mechanism for overcoming the efiect of said resilient means.

In testimony whereof, I hereunto afiix my signature, this 22nd day of January, 1929. PAUL W. BAKER. 

